Are surveillance drives good enough if one is using SSD cache?

[Saurabh Sharma]

Hello,

I am Saurabh from India. I am planning to repurpose my old computer into an Unraid server. I am a first time user. The configuration is:

i5 2500k, 24GB DDR3 RAM, ASrock Z77 Pro 3 (6 SATA ports), CM Gladiator cabinet (6 x 3.5 HDD bays + 4 x 5.25" ones), nVidia GTX560Ti 1 GB graphic card, Soundblaster sound card. 

Storage: 1TB WD black + 1TB Toshiba V300 video HDD (surveillance). 2x240GB SSD (One samsung 860 evo, other Kingston) for cache drive. I am in the market for a 4TB parity drive. If my system runs well, I will get another 4TB drive for data besides the 2 TB I have now. 

Future upgrade: Once I upgrade graphic card in my main system, GTX 10606GB will go into the unRaid system and GTX560 will be removed. 

Usage scenario: 1. Nextcloud. I will be installing and using Nextcloud on this. I have nextcloud on a Raspberry Pi 4 currently and it is enough for my needs but I still want to upgrade.

 2. Plex or some alternative for media server. Max 1-2 HD streams

 

My doubt: Why not go for much cheaper surveillance drives when we are already using cache drives? They are also meant for 24X7 operations, and are 20% cheaper in India. Are they OK as Parity drives? Or are they as good as NAS drives since I am using SSD cache and SSD cache will be written on to main drives during off hours. Won't matter much if it takes 10% more time.

Thank you

Edited November 17, 2020 by Saurabh Sharma
Spelling

[trurl]

I don't see what cache has to do with the question about reliable array disks.

[Saurabh Sharma]

Because surveillance drives are said to be reliable but slow. As per my understanding, the data that we write is written to the cache drive. It is then copied moved to the data drives in the array, so theoretically it shouldn't matter if the array drives are slow, as long as they are reliable. No?

 

Edited November 18, 2020 by Saurabh Sharma

[trurl]

1 hour ago, Saurabh Sharma said:

As per my understanding, the data that we write is written to the cache drive.

Whether and how cache is used is configured per user share:

 

1 hour ago, Saurabh Sharma said:

It is then copied to the data drives in the array

It is moved (not copied) according to the mover schedule, default is daily in the middle of the night. Note that depending on the user share setting explained in the previous link data can be move cache to array, array to cache, or not at all.

[Saurabh Sharma]

3 hours ago, trurl said:

Whether and how cache is used is configured per user share:

 

It is moved (not copied) according to the mover schedule, default is daily in the middle of the night. Note that depending on the user share setting explained in the previous link data can be move cache to array, array to cache, or not at all.

Corrected (moved, not copied). Does that mean the array data HDD I/O speed doesn't matter much for people using SSD cache (Cache only and cache preferred)? Should one spend 20% more on NAS drives when the 20% could be spent on more storage or faster SSD?

 

Came across this post on another forum:

https://www.xigmanas.com/forums/viewtopic.php?p=68007&sid=37bb585319389b7dcbd2833ff0ec6eb6#p68007

 

From what I can get, surveillance is optimized for sequential Read/Write and NAS HDD for random Read/Write. It seems surveillance HDD would be well suited as parity drives and pass off well for array operations. But those with experience with this will be able to give useful input.

Another source: https://ubernerd.com.au/desktop-vs-nas-vs-surveillance-hard-disk-drives/

Edited November 18, 2020 by Saurabh Sharma
Found additional information

[Saurabh Sharma]

I would welcome comments from experienced users on this.

Thank you

[JorgeB]

Surveillance drives are fine for Unraid, parity or data.